1. Field of the Invention
This invention relates to high pressure pulsed gas laser systems which require discharge initiation and gas flow to stabilize the glow discharge. It is specifically related to electrode assembly configurations which enhance smooth gas flow with no large scale turbulence while allowing efficient discharge initiation.
2. Description of the Prior Art
Prior electrically excited gas laser systems operated at high pressure have in many instances utilized other than uniform-field type electrode configurations. A common transversely excited atmospheric laser found in prior art literature uses discharge electrodes in a laser cavity which include a number of pin cathodes set opposite a continuous bar anode. This type of configuration has the advantage that under chosen conditions of stored energy in the pulse generator, it is possible to create a plurality of transient high current discharges between the individual pins and the continuous bar anode without an independent source of electrons to initiate the discharge. By proper spacing of the pins, the discharges merge into a homogeneous and diffuse across the entire interelectrode region. In this type of a system, the electrons for the initiation of the glow discharge are provided by field emission at the ends of the cathodic pins. The current is amplified by collisional ionization in the high field region of the gap near the pins providing large numbers of free electrons which undergo exciting collisions aand populate the upper laser levels of the gas medium. This particular electrode geometry requires a very rapid current rise time and a short glow duration in order to prevent constricted high temperature spark or arc discharge which would terminate laser action.
In an electrode assembly utilizing a non-uniform field electrode configuration, uneven distribution of current densities can result in damage by heating to the electrodes and cause discharge instabilities. Also, with non-uniform field excitation, parts of the gas volume may not be properly excited causing losses by absorption. Resultant inhomogenity of the glow discharge can have adverse effects upon the optical characteristics of the total laser system.
In other gas laser systems in which the electrode assembly has been configured to provide a uniform field discharge region, there has been no provision for smooth laminar gas flow. One prior art gas laser system utilizes auxiliary electrodes adjacent the main electrical discharge electrodes to trigger the discharge. The main electrodes, however, are positioned in an insulating enclosure with the auxiliary electrodes attached to the outer surface of the enclosure. Such a configuration does not allow for gas flow within the discharge region.
However, to operate a gas laser in a pulsed mode utilizing a uniform field electrode configuration, requires smooth laminar gas flow without major gas turbulence and some separate means for supplying initiatory electrons to the discharge region. Thus, the electrode assembly must be designed to both allow for laminar flow of the lasing gas and for efficient injection of initiatory electrons into the discharge region without interruption of the gas flow.